The present invention relates to lubricants useful with 1,1-dichloro-2,2,2-trifluoroethane (known in the art as HCFC-123). HCFC-123 may replace trichlorofluoromethane (known in the art as CFC-11) in many applications because environmental concerns over the use of CFC-11 exist.
CFC-11 is currently used as a refrigerant in closed loop refrigeration systems; many of these systems are air-conditioning systems. HCFC-123 has properties similar to those of CFC-11 so that it is possible to substitute HCFC-123 for CFC-11 in refrigeration applications with minimal changes in equipment being required.
A problem arises in such a substitution. Refrigeration systems which use CFC-11 generally use mineral oils to lubricate the compressor. We have found that the use of HCFC-123 and mineral oil results in the formation of 1-chloro-2,2,2-trifluoroethane (known in the art as HCFC-133a); in the absence of mineral oil, the use of HCFC-123 does not result in the formation of HCFC-133a. E. Long et al., Toxicol. Appl. Pharmacl., 72, 15 (1984) report that HCFC-133a is an animal carcinogen. Understandably, the potential presence of a known animal carcinogen is unacceptable in any commercial system.
Thus, an object of this invention is to substantially reduce or even eliminate the formation of HCFC-133a in HCFC-123/lubricant systems.
U.S. Pat. No. 4,851,144 teaches HCFC-123 in combination with a lubricant of 75 weight percent propylene oxide based glycol and 25 weight percent pentaerythritol tetraester of a mixture of alkanoic acids having 7 to 9 carbons. Because this glycol contains secondary hydrogens, we believe that this system would not substantially reduce the formation of 1-chloro-2,2,2-trifluoroethane for the reasons discussed below.
Kokai Patent Publication 118,598 published May 1, 1989 teaches a broad class of fluorine containing lubricants which may be used with CFC-11, CFC-12, HCFC-123, HFC-134a, HCFC-142b, HCFC-152a, HFC-23, HCFC-22, and CFC-116. This reference does not recognize the problem addressed by the present invention or suggest the present solution set forth below.
Kokai Patent Publication 115,999 published May 9, 1989 teaches that a lubricant of an alkyl benzene and a polyoxy propylene glycol monobutyl ether may be used with a hydrogen-containing medium such as HCFC-123, HCFC-134a, HCFC-142b, HCFC-152a, HFC-23, and HCFC-22. Because the alkyl benzene and glycol both contain secondary hydrogens, we believe that if this lubricating system were used with 1,1-dichloro-2,2,2-trifluoroethane, this system would not substantially reduce the formation of 1-chloro-2,2,2-trifluoroethane for the reasons discussed below.